How severe is CVE-2021-36128?

CVE-2021-36128 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-36128 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36128?

CVE-2021-36128 affects Mediawiki. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-36128?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-36128 published?

CVE-2021-36128 was published on 2021-07-02 and last updated on 2026-06-17.

CVE-2021-36128

CVE-2021-36128 is a critical-severity vulnerability in Mediawiki with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Mediawiki
Published: 2021-07-02
Last modified: 2026-06-17

Description

An issue was discovered in the CentralAuth extension in MediaWiki through 1.36. Autoblocks for CentralAuth-issued suppression blocks are not properly implemented.

Frequently asked questions

What is CVE-2021-36128?: An issue was discovered in the CentralAuth extension in MediaWiki through 1.36. Autoblocks for CentralAuth-issued suppression blocks are not properly implemented.
How severe is CVE-2021-36128?: CVE-2021-36128 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-36128 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36128?: CVE-2021-36128 affects Mediawiki. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-36128?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-36128 published?: CVE-2021-36128 was published on 2021-07-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mediawiki:mediawiki:*:*:*:*:*:*:*:*

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